Comments

A tricky one to answer without seeing an example of any particular scenario, I will try to explain how I do it sometimes.
It is possible to work with the numerical input in the properties panel by pressing the Tab key, it will highlight the spinners every time you press it giving you the opportunity to change the angle etc. you can do this in several ways.
Type in a new input and hit enter twice or click apply
Use the middle mouse wheel to click in the boxes to scroll in a change, (the angle box is a little odd with this) then enter twice or click apply.
If you turn on full dynamic geometry in the DG mode drop-down you will have the benefit of handles to change the angles of the sweep further, so, thereby using a combination of select points (F4) the snap/align tool and the shift key you will be able to click on a handle and then another point of choice to align the sweep to other scene items.
Further to this, by using the tweak tool (Q) you will be able to adjust the (bones) of the sweep in any arbitrary way you choose.
The only way to get the grasp of it is to experiment for a while.
Hope this helps.